Synthesis and characterization of Y<SUB>3</SUB>Al<SUB>5</SUB>O<SUB>12</SUB> and ZrO<SUB>2</SUB>-Y<SUB>2</SUB>O<SUB>3</SUB> thermal barrier coatings by combustion spray pyrolysis

Y3Al5O12 and ZrO2-Y2O3 (8 mol% YSZ) coatings for potential application as thermal barrier coatings were prepared by combustion spray pyrolysis. Thermal cycling of as deposited coatings on stainless steel and FeCrAlY bond coat substrates was carried out at 1000 &#176;C and 1200 &#176;C to determine the thermal fatigue response. Structural and morphological studies on Y3Al5O12 and 8 mol% YSZ coatings before and after thermal cycling have been carried out. It has been noted that the coatings on FeCrAlY substrates remain intact after 50 cycles between room temperature and 1200 &#176;C, whereas the coatings on stainless steel show some minor damage such as peeling off near the periphery after 50 cycles at 1000 &#176;C. Thermal diffusivity values of Y3Al5O12 and 8 mol% YSZ films were measured by using photo thermal deflection spectroscopy and the values are lower than those of coatings produced by conventional techniques such as EBPVD and APS